It is fairly simple to grow an orange tree with pips taken from store-bought fruit. Unlike many fruits, orange trees often come true from seed because they can produce nucellar seedlings, which are virtual clones of the mother plant. Seed-grown orange trees, however, are much slower to bear fruit than those propagated by grafting. It will usually take five to seven years for your tree to produce any oranges.
Prepare the planting tray by filling it with sterile potting soil to within an inch of the top. Add just enough water to moisten the soil.
Peel the oranges and pull them apart to locate the seeds. It's best not to slice the orange open, as this can damage some of the seeds. Immediately put the seeds on a damp paper towel to keep them moist.
Plant your seeds one to a cell in the planting tray. Push them down gently about 1/2 inch below the surface. Make sure they are covered with soil, and press down to get a good contact between the soil and seeds. Slide the tray into the plastic bag and seal it. This will keep the humidity high in the bag
Put the bag in a warm spot such as on the top of a refrigerator or cupboard. Do not place the bag near a direct heat source, as this can dry out the potting soil quickly. Check the tray every 48 hours and keep the soil moist by adding water sparingly. Germination usually occurs within 14 days.
Remove the tray from the bag after the seeds have sprouted. The sprouts need sunlight, so put them in a warm spot such as a south-facing window. Continue to keep the soil moist. When the seedlings have developed a second set of leaves they can be transplanted to the 6-inch planting containers. These should be filled with regular potting soil.
Transplant the young trees to 1-gallon containers or outside when they get too big for the 6-inch pots. For outdoor planting, you will need to live in an area with a subtropical climate such as south Florida or coastal southern California. Seedling orange trees are more cold hardy than those propagated by grafting, so you may find your new trees will do well outdoors even outside of these areas.